A nuclear spin gyroscope based on an alkali-metal-noble-gas co-magnetometer operated in spin-exchange relaxationfree (SERF) regime is a promising atomic rotation sensor for its ultra-high fundamental sensitivity.However,the fluctuation of probe light intensity is one of the main technical error sources that limits the bias stability of the gyroscope.Here we propose a novel method to suppress the bias error induced by probe light intensity fluctuations.This method is based on the inherent magnetic field response characteristics of the gyroscope.By the application of a bias magnetic field,the gyroscope can be tuned to a working point where the output signal is insensitive to probe light intensity variation,referred to herein as’zero point’,thus the bias error induced by intensity fluctuations can be completely suppressed.The superiority of the method was verified on a K-Rb-21Ne co-magnetometer,and a bias stability of approximately 0.01 °/h was obtained.In addition,the method proposed here can remove the requirement of the closed-loop control of probe light intensity,thereby facilitating miniaturization of the gyroscope volume and improvement of reliability.